The molecular basis upon which the extrapolation of carcinogenesis data obtained in animals to the human must be based, is often unknown. N-nitroso compounds, of environmental origin or endogenously produced, have been implicated in the etiology of both colon and esophageal human cancer. Aklkylation of DNA by these compounds is thought to be associated with a mutational change, possibly leading to the initiation of cancer. The main objectives of this proposal are to study the in vitro metabolism and mutagenic activation of: N-nitrosodimethylamine, N-nitrosodiethylamine, N-methyl-N-nitrosourea, 1,2-dimethylhydrazine and N-nitrosomethylbenzylamine by both the colon and the esophagus of: human, monkey, rat and mouse. In all cases, explant cultures will be used to compare the extent of DNA alkylation, CO2 production and mutagen formation (Salmonella system). Specific alkylated purines will be isolated and quantitated by high pressure liquid chromatography. To improve and speed up this latter procedure, conventional and monoclonal antibodies will be raised for use in immunoassays to be developed for O6-alkylated deoxyguanosine. Finally, human esophageal epithelial cells will be grown from explants in primary cultures. After their characterization by morphological, cytochemical and immunological methods, they will be treated with various N-nitroso compounds and monitored for transformation by examining alterations in morphology, growth rate, karyotype and ability to grow in soft agar and to produce tumors in vivo. These investigations should yield quantitative data on the interaction of N-nitroso compounds with colon and esophageal DNA of various species. These data should form a better basis for the assessment of human carcinogenic risk. Human esophageal epithelial cell lines (normal or neoplastic) can be used for further investigations of the molecular events leading to neoplastic transformation. Rapid immunoassays for alkylated DNA components have the potential for being used in the screening of tissues and body fluids of populations at risk for developing cancer because of exposure to alkylating agents.